U.S. Secretary of State John Kerry said Monday that it would be "deeply troubling" if Russia or Hong Kong had adequate notice about Edward Snowden's plans to flee to a country that will grant him asylum and still allowed him leave.

Snowden, a former National Security Agency contractor and a self-admitted leaker of state secrets, fled from Hong Kong to Moscow on Sunday after the U.S. moved to extradite him to face espionage charges. He was expected to seek political asylum in Ecuador.

He was booked on a flight from Moscow to Cuba on Monday, but he was not seen on the plane. It was unclear where he was or where he was he was trying to go, Kerry said. The U.S. has revoked Snowden's passport.

"We don't know, specifically, where he may head, or what his intended destination may be," Kerry said, responding to a question during a news conference in New Delhi where he was discussing bilateral issues between the U.S. and India.

He also was asked about whether the Snowden incident would affect the U.S. relationship with China and Russia.

"It would be deeply troubling, obviously, if they had adequate notice, and notwithstanding that, they make the decision willfully to ignore that and not live by the standards of the law," Kerry said.

"There is a surrender treaty with Hong Kong and if there was adequate notice _ I don't know yet what the communication status was. But if there was, it would be very disappointing if he was willfully allowed to board an airplane ... and there would be, without any question, some effect and impact on the relationship and consequences. With respect to Russia, likewise."

The United States does not have an extradition treaty with Russia, but does with Cuba, Venezuela and Ecuador. Even with an extradition agreement though, any country could give Snowden a political exemption.

In the past two years, the U.S. has transferred seven prisoners to Russia that Moscow wanted, he said. "I think reciprocity and the enforcement of the law is pretty important," Kerry said, but he did not identify the law he was referencing.

Kerry also noted the countries involved in the incident.

"I suppose there is no small irony here. I mean, I wonder if Mr. Snowden chose China and Russian assistance in his flight from justice because they're such powerful bastions of Internet freedom, and I wonder if while he was in either of those countries he raised the question of Internet freedom since that seems to be what he champions."